As a result of the banning of polychlorinated biphenyls (PCB's) for use as dielectric fluids in transformers (and other electrical equipment) as environmental hazards, it has been necessary to remove the PCB's already in transformers and destroy them. While the bulk of the PCB's in a transformer can be easily removed by draining the transformer, small amounts of residual PCB's are always left behind in the transformer and must also be removed and disposed of.
Typically, residual PCB's in transformers are removed using solvent flushes. That is, a solvent for the PCB's, such as mineral spirits, is repeatedly flushed through the transformer, collected, and destroyed, usually by burning. This is a hazardous and expensive procedure as it is necessary to ship the solvents containing the PCB's to disposal plants for burning. Also, it results in the loss of the solvent. Finally, this method of removing residual PCB's from transformers is not thorough enough to permit the reclamation of the materials in the transformer, and it is necessary to dispose of the entire transformer by burial under the ground.